The Canadian investor leading an effort to take BlackBerry Ltd. private is famous for making big contrarian bets that often work out.

Prem Watsa, who runs Toronto-based insurance firm Fairfax Financial Holdings Ltd. and until last month served on BlackBerry's board, is often compared with U.S. investment guru Warren Buffett. Mr. Watsa has over the years focused on beaten-up stocks—including at times, his own—and has long explained...